Ultrasonic wave propagation in heterogenous media

The non-destructive testing of austenitic steel welds using ultrasound is of vital importance for assessing safety critical structures such as those found in the nuclear industry. The internal geometry of these welds is heterogeneous and highly scattering and this makes it dicult to detect and characterise any defects within them. To help overcome these diculties the use of ultrasound transducer arrays and the associated Full Matrix Capture is becoming more widespread. There is a need therefore to develop post-processing algorithms that best utilise the data from such devices. This paper considers the use of a time-frequency domain method known as the Decomposition of the Time Reversal Operator (DORT) method. To develop this method and to demonstrate its ecacy in tackling this problem a series of simulated data sets are used. The simulated data is generated using a finite element method (PZFLEX) with the heterogeneous internal microstructure of the weld being given by previous Electron Backscatter Diraction measurements. A range of artificial flaws are then inserted into this geometry. By varying the flaw size and type a comparison is conducted between the DORT method and the Total Focusing Method (TFM) and their relative ability to perform flaw detection assessed. Importantly, however, the DORT method relies on a Singular Value Decomposition in time and frequency space and this spectral information contains information about the flaw size and shape

A Linguistic Analysis of the Entrepreneurial Pitch

An entrepreneur faces many challenges in the quest to bring an idea to fruition, and the first step in gaining financial support most commonly comes in the form of a pitch. The goal is always ultimately to persuade investors in the validity and profitability of a product or idea. A wealth of information currently exists in helping entrepreneurs create pitch content as well as giving advice on presentation skills. While this information is important for consideration, the vast majority of available knowledge hovers in the intuitive realm. Little to no quantitative, academic research exists on the actual use of language in an oral presentation. Therefore, this thesis intended to conduct a micro linguistic analysis of the entrepreneurial pitch in order to determine what linguistic devices were employed at different textual levels within the pitch that may have a yet unrecognized, but significant, impact on the decisions of investors. Borrowing theory developed by scholars like Schiffrin, Widdowson, and Lakoff and Johnson, an analysis of the syntactic structure of fourteen pitches at the word, sentence, and meta level was conducted with the intention of producing a general rubric influenced by linguistic theories and research. This study adds new insights to the growing body of research by showing what linguistic elements of an entrepreneurial pitch may affect the persuasiveness of a pitch. Advice is given concerning specific and general elements that had a quantifiable effect in the study and are useful for an entrepreneur to be aware of when crafting a pitch

Mathematical model based methods for characterising defects within ultrasonic non destructive evaluation

This thesis considers the inverse problem of detecting and characterising flaws within heterogeneous materials using ultrasonic phased array transducers. Many imaging techniques include subjective measurements and the aim of this thesis is to develop objective mathematical model based methods which alleviate such subjectivity. Within the first method, the Kirchhoff model is used to derive an explicit expression which relates the maximum eigenvalue from a scattering matrix to the length of a crack in a homogeneous medium. It is shown that there exists a one to one relationship between this maximum eigenvalue and the crack length. The advantage of deriving this analytical approximation is that it can then be analysed to assess the crack sizing capabilities of the method given some scattering matrices from experimental data (the inverse problem). The procedure for using this method is then demonstrated by applying it to finite element simulated data from a homogeneous medium with a 5 mm long crack inclusion, the crack length recovered using this method is 4.4 mm. A second method is then presented which exploits another feature of the scattering matrix. An analytical expression which is an approximation to the first minimum in the pulse echo response of a scattering matrix is derived from the Kirchhoff model. This approach is also illustrated by sizing a 5 mm long crack within a homogeneous medium from finite element simulated data, the crack length recovered using this method is 5.8 mm. The method is then extended to form a multi-frequency technique which enables it to be applied to finite element simulated data from a 5mm long crack inclusion in a heterogeneous medium. The method is enhanced by using a convolution method to reduce the noise prior to the multi-frequency method being used. The recovered crack length using this method once the noise has been reduced is 4 mm. Finally, a detection technique based on the first stage of a time reversal is presented, within which a detection threshold specific to steel welds is proposed. This method is applied to both finite element simulated data and experimental data. Having detected a flaw the time reversal algorithm (DORT) is then used to create images which are then compared to those obtained using the Total Focusing Method.This thesis considers the inverse problem of detecting and characterising flaws within heterogeneous materials using ultrasonic phased array transducers. Many imaging techniques include subjective measurements and the aim of this thesis is to develop objective mathematical model based methods which alleviate such subjectivity. Within the first method, the Kirchhoff model is used to derive an explicit expression which relates the maximum eigenvalue from a scattering matrix to the length of a crack in a homogeneous medium. It is shown that there exists a one to one relationship between this maximum eigenvalue and the crack length. The advantage of deriving this analytical approximation is that it can then be analysed to assess the crack sizing capabilities of the method given some scattering matrices from experimental data (the inverse problem). The procedure for using this method is then demonstrated by applying it to finite element simulated data from a homogeneous medium with a 5 mm long crack inclusion, the crack length recovered using this method is 4.4 mm. A second method is then presented which exploits another feature of the scattering matrix. An analytical expression which is an approximation to the first minimum in the pulse echo response of a scattering matrix is derived from the Kirchhoff model. This approach is also illustrated by sizing a 5 mm long crack within a homogeneous medium from finite element simulated data, the crack length recovered using this method is 5.8 mm. The method is then extended to form a multi-frequency technique which enables it to be applied to finite element simulated data from a 5mm long crack inclusion in a heterogeneous medium. The method is enhanced by using a convolution method to reduce the noise prior to the multi-frequency method being used. The recovered crack length using this method once the noise has been reduced is 4 mm. Finally, a detection technique based on the first stage of a time reversal is presented, within which a detection threshold specific to steel welds is proposed. This method is applied to both finite element simulated data and experimental data. Having detected a flaw the time reversal algorithm (DORT) is then used to create images which are then compared to those obtained using the Total Focusing Method

Post-retrieval propranolol treatment does not modulate reconsolidation or extinction of ethanol-induced conditioned place preference

The reconsolidation hypothesis posits that established emotional memories, when reactivated, become labile and susceptible to disruption. Post-retrieval injection of propranolol (PRO), a nonspecific ß-adrenergic receptor antagonist, impairs subsequent retention performance of a cocaine- and a morphine-induced conditioned place preference (CPP), implicating the noradrenergic system in the reconsolidation processes of drug-seeking behavior. An important question is whether post-retrieval PRO disrupts memory for the drug-cue associations, or instead interferes with extinction. In the present study, we evaluated the role of the ß-adrenergic system on the reconsolidation and extinction of ethanol-induced CPP. Male DBA/2J mice were trained using a weak or a strong conditioning procedure, achieved by varying the ethanol conditioning dose (1 or 2 g/kg) and the number of ethanol trials (2 or 4). After acquisition of ethanol CPP, animals were given a single post-retrieval injection of PRO (0, 10 or 30 mg/kg) and tested for memory reconsolidation 24 h later. Also, after the first reconsolidation test, mice received 18 additional 15-min choice extinction tests in which PRO was injected immediately after every test. Contrary to the prediction of the reconsolidation hypothesis, a single PRO injection after the retrieval test did not modify subsequent memory retention. In addition, repeated post-retrieval administration of PRO did not interfere with extinction of CPP in mice. Overall, our data suggest that the ß-adrenergic receptor does not modulate the associative processes underlying ethanol CPP

Job Satisfaction And Values Of Counselors In Private Practice And Agency Settings

Counselors can work at a variety of locations (Vacc & Loesch, 2000). Yet very little is known about each setting (King, 2007) and what type of counselors would have an optimum fit. Burnout is a pervasive issue in counseling (Lawson, 2007) and providing good-fit information could lessen turnover and burnout from the counseling field. The primary purpose of this study included investigating the differences between job satisfaction and value priorities of counselors in private practice and agency settings. The overarching theoretical framework included Frank Parsons‘ counselors, with seventy-two agency counselors and sixty-three private practitioners. Counselors completed two assessments and a survey in a descriptive correlational design. Two methods of group and e-mail administration produced a 98.7 % and 33% response rates, respectively. The data collection instruments included: The Schwartz Value Survey (SVS; Schwartz, 1992), the abridged Job Descriptive Index (aJDI; Stanton et al., 2002), the abridged Job In General Scale (aJIG; Russell et al., 2004), and the Counselor History Questionnaire (Cunningham, 2009). The statistical procedures used to analyze the data included two one-way MANOVAs and four standard multiple regressions. Post- hoc analysis included ANOVA for five subscales on the aJDI measure. The three research questions included; (a) Are there any differences between job satisfaction between counselors in private practice and agency settings? (b) Are there any iv differences between value priorities of self-transcendence and self-enhancement between counselors in private practice and agency settings?, and (c) Are there any relationships among the variables of job satisfaction and value priorities of counselors in private practice and agency setting? The first research question was supported, with private practitioners reporting statistically significant higher levels of job satisfaction on two measures, with 12.9 % of the variance explained by the model. Furthermore, the results of the post-hoc included private practitioners reporting statistically significant higher ratings on the aJDI subscales of Work and Income, and Agency counselors reporting higher scores on the Supervision subscale. The second and third research questions were not supported; as there were no differences in value priorities of counselors in private practice and agency. Furthermore, no predictive relationships existed among the variables of work location, value priorities, and job satisfaction. The data suggested that private practitioners experienced a higher level of job satisfaction than their counterparts in agency settings. Furthermore, the non-significant results of value priorities suggested that counselors, as a whole, possess similar value priorities which are not altered by different work settings. Implications for counselors and counselor educators were presented, along with areas of future research